JPS6399585A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser device incorporating a diode for preventing overvoltage, by providing the diode on a part of a semiconductor submount in parallel with the semiconductor laser element. CONSTITUTION:A semiconductor submount 11 is produced by forming a thin P-type silicon layer 13 on an N-type silicon substrate 12, photoetching the principal surface thereof so as to leave a part of the P-type silicon layer 13 unetched and vapor depositing an electrode metal to provide a diode electrode 14 on the residual P-type silicon layer 13 and to provide an upper electrode 24 of the Si submount on the exposed N-type silicon substrate 12 from which the P-type silicon layer has been removed. A semiconductor laser element 106 is mounted thereon, while a diode 10 is provided on the other part of the top face. The diode on the Si submount is adapted so as to cause reverse breakdown under a voltage higher than the operating voltage of the laser element 106 by several volts, where by no voltage higher than the reverse breakdown voltage is applied to the laser element. Accordingly, a semiconductor laser device incorporating a surge protection function can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention is applied to a semiconductor laser device having an overvoltage prevention function.

(Prior Art) Some mounting structures for semiconductor laser devices use a submount for the purpose of alleviating strain stress caused by a difference in coefficient of thermal expansion between the semiconductor laser device and a heat sink. A cross-sectional view of a mounting structure of a semiconductor laser device using this submount is shown in FIG.

In FIG. 3, 101 is, for example, a Cu heat sink;
Reference numeral 102 denotes a semiconductor submount (hereinafter referred to as Si submount), which is provided with an upper electrode layer 104a and a lower electrode layer 104b on both sides of a plate-shaped silicon substrate 103. This Si
The submount 102 is fixed to the heat sink 101 at the lower electrode layer 104b via a submount solder layer 105, and the laser element 106 is fixed to the upper electrode layer 104a via a laser element mount solder 107. There is. Note that 108 is a lead wire.

In the above mount structure, the submount material is Si, the heat sink material is Cu, and the semiconductor laser element is an example of AlG.
For the aAs system, these thermal expansion coefficients are GaAs near, (IXIO-6/deg, Si', 4.2XI
Q-'/deg, Cu: 17.0X10-6/d
eg, and the difference in thermal expansion coefficient between GaAs and Cu can be alleviated by intervening Si. By using the submount in this manner, strain stress on the semiconductor laser element can be reduced, and a highly reliable semiconductor laser device can be constructed.

(Problems to be Solved by the Invention) In a semiconductor laser device, the optical output increases exponentially when a certain voltage is exceeded. If the optical output exceeds a certain value, the end face of the semiconductor laser element will be destroyed. Therefore,
Semiconductor laser equipment uses static electricity.

Extremely vulnerable to surge voltages from drive power supplies, etc.

Although it depends on the device structure of the semiconductor laser device or the surge voltage and its pulse width, for example, when a charged voltage is applied to a capacitance of 200 pF, the withstand voltage is generally 100 to 200 μF for an AlGaAs semiconductor laser. be.

In the case of the semiconductor laser shown in Figure 3, in order to prevent overvoltage, an overvoltage prevention diode is formed in the semiconductor laser element itself, or an overvoltage prevention diode is attached externally to the container of the semiconductor laser device. It is necessary to install a diode. However, in the former case, there are many technical difficulties in forming the semiconductor laser element and the overvoltage prevention diode at the same time. In the latter case, the overvoltage prevention diode is provided externally, making it difficult to handle the semiconductor laser device.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser device having a built-in overvoltage prevention diode by forming the diode in a part of a semiconductor submount in parallel with a semiconductor laser element.

[Structure of the invention]

(Means for Solving the Problems) A semiconductor laser device according to the present invention includes a semiconductor submount having a thin metal layer on one surface, a semiconductor laser element mounted on the semiconductor submount, and a semiconductor laser device mounted on the semiconductor submount. It is characterized by comprising a diode formed in a part of.

(Function) The semiconductor laser device of the present invention includes a diode for overvoltage prevention in a part of the semiconductor submount, and prevents a voltage higher than the diode breakdown voltage from being applied to the semiconductor laser element due to static electricity, power surge, etc. be done. Further, the above-mentioned configuration allows the semiconductor laser device to be easily handled and has high reliability as a semiconductor laser device.

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. In the description, parts that are the same as in the prior art will be indicated in the drawings with the same reference numerals as in the prior art, and the explanation will be omitted.

The mount structure of an embodiment of the semiconductor laser device shown in cross-sectional view in FIG. Element 106 is mounted and a diode rule is formed on the other portion of the top surface. In the above structure, especially the configuration of the diode river, Figure 2a
-c will be described in detail. For the semiconductor submount base, a thin P-type silicon layer 13 is formed on the N-type silicon substrate 12 by diffusion or the like (FIG. 2a). Next, photoetching is performed on the main surface on the P-type silicon layer 13 side, leaving a part of the P-type silicon layer 13 (FIG. 2b). Next, an electrode metal is vapor-deposited to form a diode electrode 14 on the remaining P-type silicon layer 13, and a Si submount is placed on the N-type silicon substrate 12 exposed by removing the P-type silicon layer. A top electrode 24 is formed (FIG. 2C). An example of a semiconductor laser device actually mounted using four Si submounts U constructed as described above is shown in FIG. 1a. In this case, the polarities of the diode U formed on the silicon substrate and the laser element need to be opposite. That is, when using a Si submount formed as shown in FIG. 2, the laser device must be mounted P-down. This is because the reverse breakdown of the diode on the Si submount is used to prevent overvoltage. Therefore, when the polarity of the laser element is changed, it is only necessary to change the substrate polarity of the Si submount, and this can be easily handled. Note that 15 in the figure is a lead wire for leading out one electrode of the diode.

Next, another embodiment shown in FIG.
The type silicon layer 23 is formed by selective diffusion or selective ion implantation, which has the advantage of not requiring etching of the P type silicon layer.

〔Effect of the invention〕

This invention utilizes the reverse breakdown phenomenon of diodes to address the problem that semiconductor laser elements are extremely susceptible to forward surge voltage (current) and are damaged at a fraction of the rate of reverse surge voltage. are doing. That is, as shown in FIG. 1 or 2, by forming the diode on the Sj submount so that reverse breakdown occurs at a voltage several volts higher than the operating voltage of the laser element 106,
Even if a pulse voltage of 0 V or higher is applied, a voltage higher than the reverse breakdown voltage of the diode on the Si submount will not be applied to the laser element. Therefore, considering the I-V characteristics of the laser element, when a surge voltage is applied, the current flowing through the laser element is smaller than that of the conventional structure (Fig. 3).
can be kept several orders of magnitude lower than that of In other words, even if the same surge voltage is applied, the damage to the laser element will be much smaller than in the conventional case.

Further, the reverse breakdown voltage of the diode on the submount is determined by the type 1fi (Si) of the submount substrate.

It is possible to change the doping concentration of GaAsr and other compound semiconductors), the P layer, and the N layer to around 2 to 10 V depending on the characteristics of the laser element. This determines whether avalanche breakdown or Zener breakdown occurs depending on the doping concentration, and in the vicinity of 2 to 9 V, the Zener breakdown phenomenon due to high concentration doping is utilized.

As described above, the present invention makes it possible to construct a semiconductor laser device with a built-in surge protection function, and exhibits remarkable effects in terms of ease of handling and improved reliability of the semiconductor laser.

[Brief explanation of the drawing]

FIG. 1a is a cross-sectional view of a semiconductor laser device according to an embodiment of the present invention, FIG. 1 is a cross-sectional view of a semiconductor laser device according to another embodiment of the present invention, and FIG. Both are cross-sectional views showing the manufacturing process of the submount in the order of steps, and FIG. 3 is a cross-sectional view of a conventional semiconductor laser device.

Claims (1)

[Claims] A semiconductor laser device comprising a semiconductor submount having a thin metal layer on its surface, a semiconductor laser element mounted on the semiconductor submount, and a diode formed in a part of the semiconductor submount. .